Stretchable Electronic Facial Masks for Sonophoresis
Transdermal drug delivery has made an important contribution in the medical treatment for thousands of years. Comparatively, traditional drug delivery methods (injection or oral administration) are more suitable for systemic diseases and acute diseases requiring immediate medication, while for some local diseases, targeted release mechanism is required to reduce non target toxicity and improve the overall efficacy of treatment and thus transdermal drug delivery system has significant advantages. The strategies for accelerating the delivery of drugs mainly include conventional chemical enhancers, iontophoresis, sonophoresis, microneedles, etc. Sonophoresis, in which ultrasound is used for the delivery of drugs into/through the skin, such as glycerin, hyaluronic acid (HA), nicotinamide, nanoparticles, protein, DNA and viral vaccines. Compared with conventional chemical enhancers and iontophoresis, sonophoresis can increase the skin permeability for a broader range of molecular weight up to tens of thousands of Daltons without involving irritation or toxicity to living cells and serious skin pain. Microneedles show broadly capable of delivering not only small molecules but also macromolecules, however, they are physically invasive, which raises additional considerations about safety and sterility. The main mechanism of sonophoresis is based on the cavitation effect. Other mechanisms, such as the thermal effect, may also play nonnegligible roles in some cases.
It is a promising idea to apply the technique of sonophoresis to human facial healthcare by developing a wearable electronic device, since improving facial health conditions is of great significance for people of all ages. Researchers have designed and prepared a series of flexible/stretchable ultrasonic devices in recent years, which have great potential in medical treatment and healthcare applications. The majority of these flexible/stretchable ultrasonic devices were applied on complex surfaces for imaging/monitoring of the internal structure, such as three-dimensional images of complex defects, central blood pressure, deep-tissue haemodynamics, blood flow velocity. Besides, the therapeutic capacity, such as accelerating chronic wound healing, has also been studied recently based on such devices. On the other hand, the large-area and complex surface of human faces still brings huge technical challenges and the function of sonophoresis has not been investigated in these flexible/stretchable devices.
Recently, researchers from the Institute of Mechanics, Chinese Academy of Sciences have proposed a stretchable electronic facial mask (SEFM) as a platform for facial healthcare. As a device-level demonstration, functional components for sonophoresis are integrated on the platform for promotion of transdermal drug delivery. The SEFM consists of stretchable island-bridge mesh circuit, specially designed piezoelectric arrays with the resonant frequency of ~ 1 MHz and face-like encapsulation. Key designs and techniques developed in this work include: (1) the design of single-side structure for the piezoelectric components to achieve the low bending stiffness and high bendability, (2) the joined silicone layer by two planar half-face portions enabling the encapsulation of the planar island-bridge mesh circuit and conformal fitting the human face, (3) the SSSP technique for the encapsulation process to maintain a low stiffness of the SEFM, (4) the organic-inorganic composite structure to enhance the ductility and the robustness of the bridge interconnects, and (5) the 4-pillar design with the slender aspect for uniform sound intensity and large total power of sound field, many of which could be extended to the design and fabrication of other stretchable electronics. The mechanical, thermal, piezoelectric and ultrasonic characteristics of the components or the entire SEFM are verified by the FEA and experiments. Finally, animal skin experiments and human facial experiments verify the effect of the SEFM on accelerating the delivery of HA. Other drugs, which have been proven by the previous literatures, can also penetrate the skin more effectively by using the SEFM to achieve different therapeutic efficacy. The comprehensive results of this study indicate tremendous potential of the developed SEFM for facial healthcare applications.
Related results were published in ACS Nano (https://pubs.acs.org/doi/10.1021/acsnano.1c11181).
Display and mechanism of the SEFM.